Netgear CM1000 : No longer receiving anywhere near gigabit download speeds.

[Nexai]

Unfortunately I've been receiving approximately 20-25% the capable download speeds, averaging 200-250 mbps, with my CM1000 for approximately the last two months. I purchased the modem back in on 2/22/2020. I go through Comcast and upgraded the services to the gigabit plan back in February and was initially receiving on average 850-900+ mbps down and 35-40mbps up. The upload is still the same. I did not notice the reduced download performance until some time in May.

Things to note...

1. The CM1000 modem was purchased as new and from what I could discern is using the latest firmware V6.01.02.

2. My router is the ASUS AC1900 and is gigabit capable.
3. I've tested the speed with a direct connection to the CM1000.

4. My ethernet adapters (onboard) are the Intel 1219-V and gigabit capable, the cables are both CAT6.

5. My system specifications have not changed whatsoever and both are identical hardware ie; Win 10 Pro, i7-8700k, ASUS Maximus XI Hero motherboard, 32gb corsair vengeance 2400 ram, Samsung 970 pro ssd, etc.
6. I have not changed any of my networking components or any system software.

7. I've spoken with Comcast for the past month and a half and as one might expect it's been incredibly frustrating. They've checked and determined the following...

A. Ran diagnostics, determined an issue with download channels

B. Sent a technician to boost the line

This has been a troublesome endeavor with Comcast. They're now trying to say it's purely the modem at fault and that Netgear is the only one that can help resolve this matter.

I reset the modem just last night since it was acting sluggish. Here's a couple quick captures information via the Netgear login.

Cable Connection

https://puu.sh/G4EAE/324250f932.png

https://puu.sh/G4EB5/e13f0c31a0.png

Event Log

https://puu.sh/G4EDF/91b0be3036.png

I did open up a ticket with Netgear just moments ago. I registered the product I believe quite early on if not the same day I received it. I erroneously stated in the ticket I'd purchased it from Amazon, instead of Best Buy. I'm just so used to most of my purchases being from Amazon. Though I did upload proof of purchase shortly after with the proper invoice.

I'm simply making a post here too in case anyone has any other ideas. I want to place the blame on Comcast, since everyone knows their track record, though it is possible the hardware has simply gone bad and needs to be exchanged. I still have a functional CM600 that I could use in the interim if need be. The CM600 was always quite reliable for me and sometimes exceeded its advertised limit of 400mbps down. 

I just ideally don't want to experience any downtime at all since I do work from home and my business has always relied on my connection stability.

I appreciate the time put forward to anyone that reads this and offers some ideas of what to do or what, if anything, to communicate differently with Comcast if necessary.

[FURRYe38]

Have the ISP check the signal and line quality UP to the modem. 
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 

[Nexai]

I have indeed done the following...

1. Comcast tested the quality through numerous diagnostics. The upload performance is fine, however download performance is lacking and does show errors relating to the download channels with my modem.

2. I do not use any splitters.

3. Swapped in two new RG6 coax cables.

I put in a ticket with Netgear on 7/7 and still have yet to hear anything back unfortunately. Even prior to the pandemic I've relied on a stable connection. Power cycling my modem 3-4 times per week, for the past two months, just to have a working connection and receiving approx. 25% download capability is becoming quite frustrating. I'm hoping that a replacement can be done expediently since I'm not sure what else can be done at this point if there's no other suggestions.

Thanks for taking the time to give a response, I do appreciate it.

[FURRYe38]

While you wait for NG support to respond, can you temporarily rent a ISP modem from them and test it out to make sure a different modem works for you? 

[Nexai]

I do indeed have a different modem, the CM600. Prior to owning the CM1000 and a gigabit line I was using the 400/10 plan on Comcast and receiving adequate speeds.

I had another tech come out today. For whatever odd reason, the previous tech support agent failed to mention this. Apparently a filter has been put into place that affects all residents of the apartments I live at. As such it's degraded the quality of service for me. I understand the need for this however it's certainly awful that at least myself had to find out this way months later.

This tech was quick to end the call. I didn't get to ask if indeed the signal has been amplified or not, as I was told, since the first tech neglected to mention this major detail of the filter before. Unfortunately due to the pandemic I can't let anyone into my premises at the moment due to the high risk with my son who has immune system issues. I've got a new tech coming out on the 17th. I'm curious if anyone happens to have some extra input they could provide me that I could ask this tech? For example I'm thinking something along the lines of...

1. Was the signal boosted and by how much?
2. Can I purchase a new filter and/or splitter to either install or replace the current ones?

Things I'm unaware of are what kind of filter or splitter I might need to acquire to adequately receive gigabit speeds. To my knowledge I don't have a splitter unless it's in the wall itself. There is no splitter from the wall plate to the modem.

The connection is asynchronous at 1000/40 down and up respectively. I've been trying to do some research into moca filters and splitters though this is a bit beyond me. I'm not afraid to learn or work on a project whatsoever though. From my understanding it may be as simple as installing a filter on the existing line within the wall and it'd be good to go, though I'm aware this may not be the case.

If anyone else has any helpful suggestions or questions, especially to ask of the tech, I'd genuinely appreciate it!

[FURRYe38]

What you might do is downgrade to lower ISP speed for now. Until the 1G can be stablized for you. I would not want to pay for something that I can't have stability in. IT seems to be a ISP issue on there side rather a modem issue. IF they can't stablize the 1Gb plan then you may need to downgrade as well. Also being in a apt complex, you may have others online as well and when this happens speeds can decrease. Cable lines are effected by having more users on one line. Some to also ask the tech about if you can get a social distance contact with them. 

[Nexai]

They've just yesterday credited my account for two months worth of service due to the issues. So that's one plus at least.

I do realize I may have to ultimately downgrade although I am hoping to exhaust all options first. Something customer loyalty dept also suggested, then to call back if it doesn't work out. I do agree about the dilemma of multiple other users. However, throughout Feb, Mar, Apr I was still getting 900+/35-40 consistently in speedtests. The tech mentioned that the filter is the underlying issue overall. I'm hoping that whatever the tech wanted to come in to fix is something I can just do myself.

[FURRYe38]

Keep on them. Have the tech test your modem while he's there if possible.